Hey guys, so i'm fairly new to this thread and i'm sure plently of you have gone through what i'm about to ask. I've purchsed my drone a few months ago and i fly it every chance i get, which isn't very often. Anyways I caught on pretty quickly. Tonight I was flying my drone and everthing was working fine. I usually have my ipad hooked up to my controller but tonight I decided i'd use my phone instead. As I take off the drone starts to move sideways by it's self. I was able to control the drone to come back but as soon as i let off of the stick it would go back to the side. Than it decided to go forward on its own which i still had control of so i brought it back, but than it took a left turn and went north and i still had control and in my fliight log you can see that i'm trying to control this thing but it's trying to go another way. it went in two big circles... one from me trying to bring it home and another where it starts to go on it's own again. Anyways you can see in the flight log that I wasn't controlling it and that it was moving on it's own. So i panicked and hit the return home button, but that didn't do anything either. After flying 1800 ft away it finally stopped and i was able to control back home.... What caused it to act like that? It seriously was a fight against the machine trying to control it while it wanted to do it's own thing.

You would need to upload your flight logs to members to examine.  You could have taken off and had magnetic or other interference which causes your drone to switch to Atti mode.

http://www.phantomhelp.com/Phantom-4/#DataLog just go to this link follow instructions to upload your flight log, and come back here and post the link.
You should be able to get some info that will help you going forward.

Were you flying at dusk?

We can't see anything because you did NOT post anything...post flight logs as pointed below, what type of phone/tablets,  etc...